New palaeotemperature curve during the middle to late Permian reconstructed from oxygen isotopes based on well-preserved brachiopod shells


Climatic warming induced by CO2 injection is becoming a major concern of the sustainability of the future Earth's ecosystem. The Middle-Late Permian Earth system witnessed two major mass extinctions, which are assumed to have been related to climatic warming associated with the Emeishan Large Igneous Province and the Siberian Traps Large Igneous Province. However, reconstructing palaeotemperature changes in geological history is challenging. This is because most of the paleotemperature proxies are subject to diagenesis. Brachiopod shells are potential archives that can record the pristine geochemical signals of the past ocean due to their low-Mg content and resistance to diagenesis.

To provide a high-resolution paleotemperature curve in the Middle-Late Permian oceans, Dr. Wenqian Wang analyzed the oxygen isotopes of well-preserved brachiopod shellsfrom the Zhen’an County, Shaanxi Province under the supervision of Professor Shuzhong Shen. The preservation state of the brachiopod shells was evaluated by the Scanning Electron microscope, Cathodoluminescent microscope, and the trace and major elemental concentrations. The oxygen isotopes of the conodonts collected in the same section were also analyzed to be compared with brachiopod shells.

The comparison of oxygen isotopes between brachiopod shells and conodonts revealed that the two records are consistent in the first order, but discrepancies exist at a finer scale. Moreover, δ18O values of the conodonts have a wider range of confidence intervals in the same horizon than those of brachiopod shells. More work needs to be done to understand the difference in oxygen isotope records between brachiopod shells and conodonts. 

The palaeotemperature reconstructed from the δ18O values of well-preserved brachiopod shells showed two warming trends at the late Capitanian and the latest Changshingian, respectively. The two warming events are coeval with the onset of the Emeishan Large Igneous Province and the Siberian Large Igneous Province, respectively, suggesting that the two volcanic events are the plausible drivers of these climatic warming events. 

This study confirms that δ18O of the brachiopod shells are valuable archive for tracking chemical conditions of past oceans. The study also suggests that palaeotemperature changes have played critical roles in driving the two mass extinctions during the Middle-Late Permian.

This study was published on <<Earth and Planetary Science Letters>> entitled “A high-resolution Middle to Late Permian paleotemperature curve reconstructed using oxygen isotopes of well-preserved brachiopod shells” recently. The co-authors of this paper are Professor Feifei Zhang, vice Professor Yukun Shi in School of Earth Sciences and Engineering, Nanjing University, Dr. Claudio Garbelli, Quanfeng Zheng, Yichun Zhang, Dongxun Yuan, and Bo Chen in Nanjing Institute of Geology and Palaeontology. This work was supported by Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18000000, XDB26000000), the Natural Science Foundation of China(41420104003, 91955201, and 41830323) and CAS (QYZDY-SSW-DQC023) for SZS, WQW and CG, funding from the PIFI initiative of CAS (2018PC0042) to CG.

Reference: Wang, W.Q., Garbelli, C., Zhang, F.F., Zheng, Q.F., Zhang, Y.C., Yuan, D.X., Shi, Y.K., Chen, B., Shen, S.Z., 2020. A high-resolution Middle to Late Permian paleotemperature curve reconstructed using oxygen isotopes of well-preserved brachiopod shells. Earth and Planetary Science Letters 540.

Figure1. Carbon and oxygen isotopes of brachiopod shells from Zhen’an County, Shaanxi Province, and oxygen isotopes of conodonts from different sections.